Event logger

Features

• ~1 micro second precision
• Up to 4 source channels:
  • IMU
  • GPS
  • Image Acquisition
  • External General Purpose Input (e.g., odometer - 3..5V pulses)

Description

The FPGA-based Event Logger uses local clock for time-stamping, so each log entry (IMU, GPS, Image Acquisition and external input) is recorded with timing info.

In a single camera each acquired image has a timestamp in its header (Exif). The log entry for images has this timestamp recorded at the log (local) time.

Multiple cameras (e.g., Eyesis4Pi) are synchronized by the master camera to sub-microsecond, and each acquired also image has the master timestamp in Exif. The log entries for images (if logged in the camera other than master so with different local clock) have 2 fields - master timestamp (same as in image Exif) and local timestamp (same clock as used fro IMU), so it is easy to match images with inertial data.

A typical log record has the following format:

[LocalTimeStamp] [SensorData]
Examples or parsed records:
[LocalTimeStamp]: IMU: [wX] [wY] [wZ]  [dAngleX] [dAngleY] [dAngleZ] [accelX] [accelY] [accelZ] [veloX] [veloY] [veloZ] [temperature]
[LocalTimeStamp]: GPS: [NMEA sentence]
[LocalTimeStamp]: SRC: [MasterTimeStamp]

Is used in Eyesis and Eyesis-4PI. Can be used with any other Elphel camera.